The present invention relates to a portable telephone with attenuation for surrounding noise.
Portable appliances are known, in particular headsets, that are fitted with active anti-noise circuits designed to compensate surrounding noise by delivering to the earpiece of the headset a signal that is in phase opposition with a signal representative of surrounding noise. The representative signal is picked up by means of an anti-noise microphone specially dedicated to this function or by means of an extractor filter connected in parallel with the output from a speech microphone associated with the headset. In both cases, the microphone for picking up surrounding noise is disposed in a particular manner that is not transposable to a portable telephone. Also known, in particular from document EP-A-0 661 903, is a portable telephone in which decoupling between surrounding noise and the wanted signal issued by the earpiece is provided by means of a first anti-noise microphone adjacent to the earpiece and a second anti-noise microphone opening out through a face opposite from the earpiece. Such a circuit is complex and expensive.
The invention provides a portable telephone comprising both a case fitted with an antenna and pierced by communications openings in one face associated with a speech microphone and with an earpiece, and an anti-noise microphone connected to the earpiece via an active anti-noise circuit, the anti-noise microphone being associated with at least one opening that is separate from the communications openings of the speech microphone and of the earpiece, and the anti-noise microphone being a directional microphone directed towards the associated opening.
Thus, even when the anti-noise microphone is placed close to the earpiece of the portable telephone, speech signals in the earpiece or speech signals from the user are picked up by the anti-noise microphone with a large amount of attenuation, such that the anti-noise circuit serves to attenuate only ambient noise without attenuating the signals forming part of the conversation, and while using only a single anti-noise microphone.
In an advantageous feature of the invention, the opening associated with the anti-noise microphone opens out through a point of the case that is remote from the antenna. Thus, the slot between the battery block and its housing allows surrounding noise to pass through anywhere along the outlet slot, such that there exists very little risk of this entire slot being covered by the hand of the user.